Isolation of DNA from single microsurgically excised bands of polytene chromosomes of Chironomus

A method is described for excising by a glass knife single bands of isolated polytene chromosomes of the salivary glands of Chironomus tentans larvae. DNA strands were isolated from cut-out bands and their contour lengths were determined on electron micrographs. The mean contour length of DNA strands isolated from the double band I-8A was about twice that of the single band I-11B, namely 63 versus 34 micrometers. The described method may be applicable for molecular studies on single bands (e.g., by DNA cloning).